Optical coherence tomography (OCT) is a high-resolution cross-sectional imaging tool that has become important in diagnosing ocular and other medical diseases (Huang D et al, Science 254, 1178-1181 (1991); incorporated by reference herein.) In OCT, the depths of sample reflections are measured indirectly by interference with a reference reflection. OCT provides both high detection sensitivity (photon shot-noise limited) and high resolution (better than 10 μm). It is often implemented with fiber optics for ease of alignment, compactness, modularity, and stability. The imaging speed of OCT has been improved greatly with the development of the Fourier domain (FD) technique (Wojtkowski R et al, J Biomed Opt 7, 457-463 (2002): de Boer J F Opt Lett 28, 2067-2069 (2003); and Choma M A et al, Opt Express 11, 2183-2189 (2003); all of which are incorporated by reference herein) making it possible to use OCT for clinical applications.
Catheter-based imaging has extended the use of OCT to blood vessels (Fujimoto J G et al, Heart 82, 128-133 (1999) and Yang X D et al, Opt Express 11, 2416-2424 (2003); gastrointestinal tracts (Rollins A M et al, Opt Lett 24, 1358-1360 (1999) Izatt J A et al, IEEE J Selected Topics Quantum Electron 2, 1017-1028 (1996); both of which are incorporated by reference herein) respiratory tracts (Pitris C et al, Am J Respir Crit Care Med 157, 1640-1644 (1998), incorporated by reference herein), and genitouninary tracts (Yaqoob Z et al, J Biomedical Optics 11, 063001-1-19 (2006); incorporated by reference herein.) OCT has proved useful in guiding some important endoscopic procedures, such as fine needle aspiration and endoscopic mucosal resection. OCT angioscopy has higher resolution than X-ray and ultrasound and can detect atherosclerotic plaques vulnerable to rupture. Miniature side-scanning OCT catheters have been successfully used for coronary angioscopy (Schmitt J et al, European Cardiology May, 2005).